This invention relates generally to an apparatus for multiplexing a plurality of hydraulic cylinders and, more particularly, to an apparatus for diverting hydraulic fluid flow to selectively multiplex a plurality of hydraulic cylinders.
Hydraulic systems are used to perform a wide variety of tasks. For example, hydraulic systems, in particular, electro-hydraulic systems, are used to provide the power needed for machines such as backhoe loaders, excavators, wheel loaders, track-type tractors, and the like to perform earthworking operations.
Machines such as the above have become increasingly more complex and sophisticated. A backhoe loader, for example, requires hydraulic power for several functions, such as swing, boom, stick, bucket, auxiliary, stabilizers, and such. The demands placed on a hydraulic system may exceed the power output available by the system. Therefore, systems have been designed which share, i.e., multiplex, operations. For example, control of tilt and swing cylinders may be multiplexed.
Multiplexed hydraulic systems require some means to control the flow of hydraulic fluid to the desired cylinders. Consequently, many valves have been developed to selectively divert hydraulic fluid to the desired location. These valves, however, add cost and complexity to the hydraulic system. The potential for mechanical problems, and the higher associated costs with parts replacement, create additional concerns for an equipment operator who must optimize productivity and minimize costs.
It is therefore desired to provide hydraulic multiplexing with divertor valves that are low cost and readily replaceable. It is also desired to provide divertor valves that are not complex in design or construction, and therefore are less prone to mechanical failure.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention an apparatus for multiplexing a first hydraulic cylinder and a second hydraulic cylinder is disclosed. Each cylinder has a head end port and a rod end port. The apparatus includes a tank, a pump connected to the tank, and a control valve having an inlet port connected to the pump, an outlet port connected to the tank, and first and second control ports. The apparatus also includes at least two two-position valves each having at least one port connected to a corresponding at least one of the first and second control ports and at least one other port connected to a corresponding one of the head end and rod end ports of the first and second hydraulic cylinders, the at least two two-position valves being operable to selectively divert hydraulic fluid from the respective first and second control ports of the control valve to one of the first and second hydraulic cylinders.